To provide a desirable appearance over their useful life, mattresses should avoid having a depression therein in the central portion of the mattress. In order maximize the desirability of that appearance, mattresses should at a minimum appear flat or more preferably have a slightly crowned shape. In the latter case, mattresses maybe configured so that a central portion of the mattress is higher than the end portions resulting in a crown of the mattress in the central portions. These crowned mattresses typically employ a wire frame having two substantially flat and parallel planes with a plurality of spring members disposed between the two planes. One or more layers of resilient material, such as foam, are placed on the planes. The foam layers may be tapered such that they are thicker in the middle and thinner as they extend outwardly toward the peripheral edges. This configuration causes the middle section of the foam to be thicker than around the edges and provides a crowning of the mattress. The resilient material can be configured so that the mattress crowns between peripheral edges that define the length of the mattress and/or crowns between peripheral edges that define a width of the mattress.
Loading on a mattress (by a person sitting or lying on the mattress) is usually located in a central portion of the mattress and is not concentrated along or adjacent to the peripheral edges of the mattress. That is, the central portion of the mattress over time will experience the most loading and, as a result, experience the most compression. Over time, this concentrated loading in the central portion of the mattress may result in diminished comfort in the central portion and may cause the resilient material in the central portion to break down. With the loading concentrated in the central portion, it is desirable that the central portion provide the most comfort for a user of the mattress along with being capable of supplying the comfort level over the lifespan of the mattress.
As the mattress gets used, the loading causes the resilient material to break down, especially in the central portion, and the crowning effect is diminished. After a period of usage, the crowning effect is so diminished that an undesirable appearance of the mattress occurs. Specifically, the breaking down of the resilient material may result in a depression in the mattress that provides an undesirable appearance. Additionally, the spring members in the central portion of the mattress may also exhibit a loss of resiliency and contribute to the formation of a depression. This undesirable appearance is especially problematic in the hospitality industry where the appearance of the mattress is important to customer satisfaction. As a result of the undesired appearance, the hospitality industry typically replaces the mattress.
The breaking down of the resilient material and the onset of a depression, however, typically occurs prior to the end of the useful life of the mattress. In other words, the crowning effect is lost and the undesirable appearance occurs prior to the end of the useful life of the mattress. Thus, the hospitality industry replaces the mattress due to the undesirable appearance prior to the end of the useful life of the mattress. The replacing of the mattress due to the undesirable appearance prior to the end of the useful life is expensive. Such replacement not only comprises the cost of a new mattress, but also the cost of labor in installing a new mattress and removing the old one as well as the cost of disposing of the old mattress.
Accordingly, it is advantageous to provide a crowned mattress that remains crowned for a prolonged period of time and does not rely solely upon the structural integrity of the resilient material to maintain the crowned appearance. Furthermore, it is also advantageous to reinforce the central portion of the mattress in order to increase the comfort and/or the longevity of the central portion of the mattress.